Rare earth magnets composed mainly of intermetallic compounds of rare earth elements with transition metal elements such as Fe and Co have a high magnetocrystalline anisotropy, and thus are widely used in consumer, industrial, and transport machinery and apparatuses and the like as a high-performance permanent magnet. In recent years, the demand for miniaturization of various kinds of electrical machinery and apparatuses has increased, and high-performance permanent magnets exhibiting higher magnetic properties have been desired in order to cope with this demand.
Rare earth permanent magnets containing a tetragonal R2T14B compound (“R” represents a rare earth element, and “T” represents Fe or Fe that is partially substituted with Co) as the main phase are known to exhibit excellent magnetic properties, and have been a typical high-performance permanent magnet after being invented in 1982 (Patent Document 1).
R-T-B based permanent magnets in which the rare earth element “R” is Nd, Pr, Dy, Ho, or Tb have a great anisotropic magnetic field Ha, and thus they are preferred as a permanent magnet material. Among them, Nd—Fe—B based permanent magnets in which the rare earth element R is Nd have a saturation magnetization Is, the Curie temperature Tc, an anisotropic magnetic field Ha in good balance, and thus are widely used.
In addition, Patent Document 2 proposes a magnetic material having a high Fe concentration in the main phase and a high saturation magnetic flux density for a permanent magnet that contains an R-T compound having a TbCu7 type crystal structure as the main phase.
Furthermore, Patent Document 3 proposes a magnetic material having the highest Fe concentration in the main phase among the permanent magnets whose main phase is an R-T compound having a ThMn12 type crystal structure. Non-Patent Document 1 reports that the Nd(Fe0.93Co0.02Mo0.05)12Ny thin film in which the crystal structure of the main phase grains is a ThMn12 type has a high saturation magnetic flux density of 1.62 T and a high coercivity of 693 kA/m.
Meanwhile, the consumption of rare earth elements that are a rarer element is increasing, and thus a magnet using an element abundant in resource among rare earth elements is desired in terms of price and stable supply.